From 33c54ee6fd63189be96e237cd85b99aedf0e0770 Mon Sep 17 00:00:00 2001
From: Robert Chou <robert.ch.chou@acer.com>
Date: Thu, 13 Jul 2017 20:50:40 +0800
Subject: [PATCH] net: zoap: advance block context by checking M bit from block
 option

According to RFC7959 page 30, "The end of a block-wise transfer is
governed by the M bits in the Block options, _not_ by exhausting the
size estimates exchanges."

Therefore, we should check the M bit instead of total size (which
is not always available, too)

Signed-off-by: Robert Chou <robert.ch.chou@acer.com>
---
 include/net/zoap.h                        |  4 +++-
 samples/net/zoap_server/src/zoap-server.c |  2 +-
 subsys/net/lib/zoap/zoap.c                | 12 ++++++++++--
 tests/net/lib/zoap/src/main.c             |  2 +-
 4 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/include/net/zoap.h b/include/net/zoap.h
index b655fd0866f..19357daa577 100644
--- a/include/net/zoap.h
+++ b/include/net/zoap.h
@@ -687,12 +687,14 @@ int zoap_update_from_block(const struct zoap_packet *zpkt,
  * indicates the correct offset in the body of data being
  * transferred.
  *
+ * @param zpkt Packet in which to look for block-wise transfers options
  * @param ctx Block context to be updated
  *
  * @return The offset in the block-wise transfer, 0 if the transfer
  * has finished.
  */
-size_t zoap_next_block(struct zoap_block_context *ctx);
+size_t zoap_next_block(const struct zoap_packet *zpkt,
+		       struct zoap_block_context *ctx);
 
 /**
  * @brief Returns the version present in a CoAP packet.
diff --git a/samples/net/zoap_server/src/zoap-server.c b/samples/net/zoap_server/src/zoap-server.c
index 73a61216323..caf8e588c98 100644
--- a/samples/net/zoap_server/src/zoap-server.c
+++ b/samples/net/zoap_server/src/zoap-server.c
@@ -656,7 +656,7 @@ static int large_get(struct zoap_resource *resource,
 		return -EINVAL;
 	}
 
-	r = zoap_next_block(&ctx);
+	r = zoap_next_block(&response, &ctx);
 	if (!r) {
 		/* Will return 0 when it's the last block. */
 		memset(&ctx, 0, sizeof(ctx));
diff --git a/subsys/net/lib/zoap/zoap.c b/subsys/net/lib/zoap/zoap.c
index 4fd05f66eec..f86fadf19f9 100644
--- a/subsys/net/lib/zoap/zoap.c
+++ b/subsys/net/lib/zoap/zoap.c
@@ -1270,9 +1270,17 @@ int zoap_update_from_block(const struct zoap_packet *zpkt,
 	return update_descriptive_block(ctx, block2, size2);
 }
 
-size_t zoap_next_block(struct zoap_block_context *ctx)
+size_t zoap_next_block(const struct zoap_packet *zpkt,
+		       struct zoap_block_context *ctx)
 {
-	if (ctx->current >= ctx->total_size) {
+	int block;
+	if (is_request(zpkt)) {
+		block = get_block_option(zpkt, ZOAP_OPTION_BLOCK1);
+	} else {
+		block = get_block_option(zpkt, ZOAP_OPTION_BLOCK2);
+	}
+
+	if (!GET_MORE(block)) {
 		return 0;
 	}
 
diff --git a/tests/net/lib/zoap/src/main.c b/tests/net/lib/zoap/src/main.c
index 479433faf15..ad0b36cbb29 100644
--- a/tests/net/lib/zoap/src/main.c
+++ b/tests/net/lib/zoap/src/main.c
@@ -997,7 +997,7 @@ static int test_block_size(void)
 	net_pkt_unref(pkt);
 
 	/* Let's try the second packet */
-	zoap_next_block(&req_ctx);
+	zoap_next_block(&req, &req_ctx);
 
 	pkt = net_pkt_get_reserve(&zoap_pkt_slab, 0, K_NO_WAIT);
 	if (!pkt) {